Align vertices in a line NOT in axes
It appeared that the problem is easily solvable by creating the edge between two extreme verts by F and then subdividing that edge, so it has the corresponding number of verts. Then simply slide the verts of the edge with double G with enabled snapping to vertex, so every new verts are aligned with the verts that need to be straigtened. Lastly i managed to get perfect straight edge of verts by merging them!

Thanks Mr Zak for the hint!

Also i've found a nice plugin shipped with blender - Loop Tools. It has a tool named "Flatten". It also performs fine in this situation.